1. Field of the Invention
The present invention relates to a device which recognizes such information as characters and voice and, in particular, to an information recognition device which is controlled based on characters and voice to be recognized and accordingly achieves an effective reduction of power consumption.
2. Description of the Background Art
For battery-driven mobile information terminals that have recently been increasing in number, the battery time is considered as an important factor and thus reduction of the power consumption of the devices is an essential challenge in development. Then, there arises a severer requirement for reduction of the power consumption of a character recognition device and a voice recognition device that are incorporated into the mobile information terminals. Japanese Patent Laying-Open No. 7-244494 discloses a voice recognition device capable of recognizing voice in operating with low power consumption. This voice recognition device includes: a pre-processing circuit receiving an input voice to transmit feature pattern data containing a feature amount in a voice section of the input voice signal; similarity comparison and determination circuit connected to the pre-processing circuit to compare, in terms of similarity, the feature pattern data with reference pattern data for a plurality of voices that is stored in advance to determine the degree of similarity therebetween, based on a clock signal; and a control circuit having its input connected to the pre-processing circuit and the similarity comparison and determination circuit and having its output connected to the similarity comparison and determination circuit to decrease the frequency of the clock signal lower than a reference frequency if the resultant determination as to the similarity does not indicate a predetermined voice candidate or no voice is input in at least a certain time period.
The above voice recognition device can reduce the power consumption by decreasing the frequency of the clock signal lower than a reference frequency thereby decreasing the operating speed of the similarity comparison and determination circuit when, for example, no voice is input in at least a certain time period. Even if the similarity comparison and determination circuit operates with the reduced power consumption, it can still recognize voice since the clock signal is provided to the circuit.
The disclosed voice recognition device decreases the frequency of the clock signal lower than a reference frequency when a predetermined voice candidate cannot be obtained or no voice is input in at least a certain time period. For the battery-driven mobile information terminal, more delicate power control is necessary in order to extend the battery time. As the mobile information terminal has increased functions, the operating frequency of a microcomputer provided in the mobile information terminal becomes higher, which tends to result in increase in power consumption. Therefore, the control as disclosed in the above patent document cannot achieve delicate power control in operation and is thus unsatisfactory as a measure to decrease the power consumption.